1. Field of the Invention
This invention relates to new expandable styrene-maleic anhydride copolymer particles and a process for molding the same. According to the present invention, there is provided novel expandable styrene-maleic anhydride copolymer particles in which the base copolymer is modified with a hydroxy compound containing from two to four active hydroxy groups and which are useful in the production of various foamed articles, and a method of molding said expandable copolymer particles whose use amount can be considerably saved.
2. Description of the Prior Art
Styrene-maleic anhydride copolymers containing 2-25 w/w% of maleic anhydride component to be used as the base resins of the present invention have a higher heat deflection temperature than that of conventional polystyrenes and are expected to be utilized in various fields which require thermal stability.
The production of foamed articles from said copolymer resins has been achieved by extrusion but was difficult by so-called bead molding. For this reason, there has been a proposal of reacting the copolymer, with monovalent alcohol to obtain expandable particles usable for bead molding (U.S. Pat. No. 3,742,103). However, the resulting expandable particles gave pre-expanded particles having a comparatively low bulk density upon pre-expanding but needed to charge an excessive amount of the pre-expanded particles in cavity when required for bead molding.